From d20eaa1427e3b6b0584c49ce0e86185bb594d06b Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Miloslav=20=C4=8C=C3=AD=C5=BE?= <tastyfish@seznam.cz>
Date: Sat, 17 Nov 2018 17:18:55 +0100
Subject: [PATCH] Fix a bug

---
 s3l.h     | 10 +++++++---
 testSDL.c | 36 +++++++++++++++++++-----------------
 2 files changed, 26 insertions(+), 20 deletions(-)

diff --git a/s3l.h b/s3l.h
index 6ee95b5..d983ec2 100644
--- a/s3l.h
+++ b/s3l.h
@@ -188,14 +188,18 @@ void S3L_drawTriangle(int16_t x0, int16_t y0, int16_t x1, int16_t y1, int16_t x2
     lErrAdd, rErrAdd,   // error value to add in each Bresenham cycle
     lErrSub, rErrSub;   // error value to substract when moving in x direction
 
+  int16_t helperDxAbs, helperDyAbs;
+
   #define initSide(v,p1,p2)\
     v##X = p1##PointX;\
     v##Dx = p2##PointX - p1##PointX;\
     v##Dy = p2##PointY - p1##PointY;\
+    helperDxAbs = S3L_abs(v##Dx);\
+    helperDyAbs = S3L_abs(v##Dy);\
     v##Inc = v##Dx >= 0 ? 1 : -1;\
-    v##Err = 2 * v##Dx - v##Dy; \
-    v##ErrAdd = 2 * S3L_abs(v##Dx);\
-    v##ErrSub = 2 * S3L_abs(v##Dy);
+    v##Err = 2 * helperDxAbs - helperDyAbs;\
+    v##ErrAdd = 2 * helperDxAbs;\
+    v##ErrSub = 2 * helperDyAbs;
 
   #define stepSide(s)\
     while (s##Err > 0)\
diff --git a/testSDL.c b/testSDL.c
index eaddf2a..a6fce61 100644
--- a/testSDL.c
+++ b/testSDL.c
@@ -40,31 +40,33 @@ void drawPixel(S3L_PixelInfo *p)
 const int16_t test_coords[] =
   {
     100,100, 99,101,    101,101,  // 0, small triangle
-    90,50,   100,10,    300,80,   // 1, arbitrary
-    100,30,  20,50,     40,80     // 2, arbitrary
+    190,50,  200,10,    400,80,   // 1, arbitrary
+    40,80,   20,50,     100,30,   // 2, arbitrary
+    300,300, 290,400,   310,400,  // 3, regular
+    105,300, 120,300,   201,300,  // 4, horizontal line
+    400,300, 400,320,   400,400   // 5, vertical line
   };
 
 void draw()
 {
   clearScreen();
 
-int c = 0;
+  for (int c = 0; c < 4; ++c)
+  {
+    int
+      x0 = test_coords[6 * c],
+      y0 = test_coords[6 * c + 1],
+      x1 = test_coords[6 * c + 2],
+      y1 = test_coords[6 * c + 3],
+      x2 = test_coords[6 * c + 4],
+      y2 = test_coords[6 * c + 5];
 
-  int
-    x0 = test_coords[6 * c],
-    y0 = test_coords[6 * c + 1],
-    x1 = test_coords[6 * c + 2],
-    y1 = test_coords[6 * c + 3],
-    x2 = test_coords[6 * c + 4],
-    y2 = test_coords[6 * c + 5];
+    S3L_drawTriangle(x0,y0,x1,y1,x2,y2);
 
-  S3L_drawTriangle(x0,y0,x1,y1,x2,y2);
-
-/*
-  setPixel(x0,y0,255,0,0);
-  setPixel(x1,y1,255,0,0);
-  setPixel(x2,y2,255,0,0);
-*/
+    setPixel(x0,y0,255,0,0);
+    setPixel(x1,y1,255,0,0);
+    setPixel(x2,y2,255,0,0);
+  }
 }
 
 int main()